Acute urticaria develops over days to weeks and presents with transient wheals. Generally, acute urticaria resolves within 6 weeks, whereas chronic urticaria lasts longer. Common triggers include medications (penicillin, aspirin, and NSAIDs), foods (chocolate, shellfish, nuts, eggs, milk, and others) infections (streptococcal, hepatitis B and C, mononucleosis, and helminths), and physical factors (exercise, pressure, cold, vibratory, and solar induced).
Dermatographism is the production of linear urticarial lesions and surrounding erythematous flare after stroking the skin. Simple dermatographism, seen in up to 5% of the population, is considered an exaggerated physiologic response to friction. In contrast, symptomatic dermatographism presents without a previous history. Wheals are typically seen with scratching and friction from tight clothing. Children and young adults are commonly affected, and fortunately, no associated systemic disease, autoimmunity, or food allergy exists. Symptomatic dermatographism can persist for several years.
Acute Urticaria. Classic raised plaques on the lower extremity. (Photo contributor: James J. Nordlund, MD.)
Acute Urticaria. Preschool child with annular, raised pruritic lesions with central clearing and tense edema. The lesions disappeared approximately 5 minutes after presentation. (Photo contributor: Kevin J. Knoop, MD, MS.)
Acute Urticaria and Anaphylaxis. Raised facial plaques in a patient severely allergic to bee stings. (Photo contributor: Alan B. Storrow, MD.)
Cold Urticaria. Plaque formation after placement of an ice cube on the skin confirms cold urticaria. (Photo contributor: James J. Nordlund, MD.)
Dermatographism. Linear wheal with surrounding erythematous flare after scratching and stroking. (Photo contributor: J. Matthew Hardin, MD.)
Management and Disposition
Triggers of urticaria should be investigated and, if present, stopped. H1 and H2 blockers usually help. Systemic steroids and epinephrine are used for severe reactions and anaphylaxis.
More than 50% of chronic urticaria is idiopathic; consider an infection, medication, or physical factor first.
Wheals present for over 24 hours and in the same location are concerning for urticarial vasculitis (see related item) and should prompt dermatology consultation. Draw a circle around the lesions and have the patient monitor changes.